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PROFILE

An aggressive design formanufacturing programhelped make this bird themost sophisticated heavy­equipment transport planein the world

All1aXill1 Um gro ss weig ht of585, 000 Ib (263,250 kg) attakeoff might also make theUS Air For ce's McOonu cl l

Douglas - 17 Globcmasicr III one ofthe heaviest transport planes in theworld, but don 't let that Slati tic foolyou. This aircraft is no Spruce Goose.

Th e C- 17 has se t a tota l o f 22wor ld reco rds, including tho se forpayload to alt itude, time to climb,and sho rt takeoff and landing. OneC-17 took off in less than 1400' (427m), carrying a 44,000-lb C19,800-kg)payload to altitude and land ing inless th an 14 00 ' (4 2 7) . Wi t h a160 ,000-lb (n,500-kg) payload , thep lane can ta ke off from a 7600 '(23 16-m) airfield , fly 2400 nau ticalmiles, and land on a small airfield in3000 ' (9 14 111) . Its maximum pay­load is 171,000 lb (77,5 00 kg).

Th e high -wing, four-engine , T­tailed aircraft is 174 ' (53-m) longand 55 .1 ' (17 -m) hig h, and has a169 .S· (52-m) wingspan . Hangingfrom pylons ahead of and below thewing's leading edge, each of the [ourPratt & Whitney P\V200 0 series tur­bofans produces 40,700-lb (lSI-kN)thrust. The eng ines have directed ­now thru st reversers that can deployin- Flight . Th e po wer ed -l ift sys te mdirects the engine exhaust throughdouble-slotted fl aps to produ ce theextra lih force necessary fo r stee p,low-speed final approaches and shortrunways.

The Defense Dept . has approvedprocu rement of 120 - 17s, and , sofar , has placed o rde rs 1'01' 40 lromMcfx mn cll Douglas, the prime con ­tractor. As of February, the Air Forcereceived 25 of the versa ti le cargoplanes, some of which arc now pro­viding critical support for OperationJoint Endeavor in Bosn ia and landingon ru nways ina ccessible to othe rheavy equipm ent transports.

Th e flyaway cos t is 53 25 mil ­lion/plane for the fi rst 40 airc raft . butwill drop to less than $ ] 75 million/p lane fo r the nex t SO. How hasMcDonnell Douglas been able to cutth ose costs b y nea r ly ha lf7 Byreth inking its manufacturing pro ­cesses and streamlin ing the design

and manufacture o f key assemblystru ctures.

Landing-Gear Pod RedesignOver th e las t two yea rs , the

defense cont racto r has put consider­able effort into imp roving the C-17prod uction line. A critical assemblyben efi tin g fro m this effort is themain -landi ng-gear pod, which islonge r th an th e F- I 'j fighte r. At­taching this assembly to the aircraftha s been prob lc mut ic 11'0 111 th ebeginnin g. Assembling the pod , basi­cally an aerodynam ic cove ring forthe landing gcar , occu rs in SI. Louis.but the operat ion mating it to the e­17 fuselage is at ~ I Lung Beach, CA,facility, The procedu re consumed anexcessive num ber of hou rs in assem­bly , rework , and repai r , wh ich iswhy the pod became a pr ime cand i­date for review using design for man­ufactur ing , th en a re lati vel y newtechnique for McDonn ell Douglas.

Ta rget ed for rev ision were thelarge bu lkh ead s around the gea r,which engineers redesigned to allowhigh-s peed mac hin ing. Per bu lk­head , the ability to hog out wo rkmate ria l fast allowed enginee rs toprodu ce more-com plex large single­piece co m pon en ts in an adequa tetime fram e . Before , th ey had to

machin e several smaller sections and

90 JULY 1 99G-MANUFACTURING ENGINEERING

High-Spee d~Mra&h ,i,ning :oGuts Costs

McDonnell Douglas engineersreport high-speed machining

is the key to a number of produc­tion improvements made on theC- 17. Instead of building upassemblies, the process allowsthem to produce monolithic largeparts. The first high-speedmachining application was onbulkheads in the cargo door, andthe company has since adoptedthe practice for other sections ofthe aircraft.

An example is a landing gearbulkhead machined at McDonnellDouglas Aerospace (Sl Louis) ona Giddings and Lewis five-axisgantry mill. The machine has an 8X 35 ' (2 X 11 m) bed andopposing spindles that can runtwo jobs independently. This sizemachine was necessary toaccommodate the raw workmaterial, which was a 9 X 12.5 '(3 X 4 rn) 3S (89 mm)-thick7050-T7351 aluminum alloyplate pocketed on both sldes,

Engineers rough-machinedthe bulkhead with a T (51 mm)cutter at 200 sfm (6 1 m/min)

assemble them . The redesign redu cedde tail parts from 72 to 2 and fasten ­ers from 1720 to 35.

The redesi gn al so changed thepod from a three-pi ece co m posite­skinned assembly to on e unit . Keyto red ucing assembly lime was th estep revising the attach men t method .Engineers rep laced the existing shearclip aua chrnc ms an d multiple fasten ­ers w ith a cle vis and drag- li n ka rrangemen t . Instead of riveting askate angle to the assembly's perime­ter and to the aircraft fuselage. pro ­d uctio n workers now install bladeseals that need no auachmcnt to thefuse lage. whi ch reduces the numb erof holes they must d rill th rough thefuselage and makes it easie r to com­plet e the asse mbly's int erio r work .suc h as installing insu latio n.

Before the rede sign , pod sectionsarrived from St. Louis with compos­ite cove r panels installed . In Long

and 10,000 rpm. The finalmachining process used a 3/4·(19 mm) cutter at 150 sfm (46m/min) and 13,500 rpm, andthen a 1/T (12 mrn) cutter at100 sfm (30 m/min) and 13,500rpm.

Machining one side of thebulkhead took four shifts, theother side two in a three-day peri­od. McDonnell Douglas machin­ing experts estimate the high­speed techn ique made the overallmachining time 15 X faster thanconventional machining. Accuracyalso was high. Out of the f irst 20tryout parts, engineers deter­mined 17 were accurate enoughfor installation on the aircraft.

McDonnell Douglas officialsattributed the smooth transition tohigh-speed machining to the useof Integrated Product Teams. Inone case, a team received apiece of raw material that was toosmall. Because the McDonnellDouglas personnel involved wereworking closely with the materialsupplier, the team obtained newmaterial in hours, instead of days.

Beach . worke rs had to re move th epanels to install the required lightingand hydrau lic sys tems . They thenhad to reassemble the panels. Now .workers in St. Louis install the light ­ing and hydrauli cs systems . Matingthe landing gear pod assem bly to thefusel age ta kes less l ime . and thewho le s t ruc tu re has mo re rigidi lyand a bcu cr fit.

The p roj ect showed th e impo r­ta nce of Mc Don nell Do ugla s 'sIruc gra ted Project Team sysic rn,wh ich the company put in place toen sure th a t a ll necessary g roups .from accountan ts to suppliers andmain tenan ce sta ff. p rovid e in putabout de s ign and process cha nges .The landing-gear pod redesign pro­ject , for ins tance . involved bot h 51.Louis and Lon g Beac h pe rso nn e lfrom stru ctu ra l and syste ms engi ­neeri ng . an d too ling produ ct ion . aswell as s u p p lie rs and th e product

maint enance support organization .Si nce th e redesign project

invo lved teams in both cities , a betterway to communicate was esse ntial.The solutio n involved developing aCAD model of the development fix­ture previously used to mocku p theasse mbly and verify fit of all compo­nen ts . Engineers in bot h 51. Lou isa nd Lo ng Beac h cou ld th en workwit h th e sa me elec t ro nic fixt u remod el and receive auto matic updateso f approved d esign cha nges . Th ise lec tronic design and veri ficatione li minated th e need to build twodevelopment fixtures, which hel pedreduce variation .

The cos t estimate for implement ­ing the improvements is $4 1 million .The results have led to major proce­dural cha nges that have cu t manu­facturing time by 10 days and th atwill save more tha n $ 100 mill ion onthe remaining aircraft to he deliveredto the Air Force .

Eliminate Those FastenersAnother redesign that saved time

was a project revising the original air ­craft ceiling st ructure of rnatrixed alu­minum hat-section beams. In the lirstplan es off th e assembly lines , engi­neers attached panels to the struc tureusing 24 adjustable rods . Fitting andtr imm in g th em aro un d th e ducts ,elect rical po wer centers, and avionicsra c ks wa s t im e -co nsum ing . T heredesign eliminated the ceiling struc­ture , using existing aircraft compo­nents like the ventilation du cts andfluorescent light fixture s as support.Inst ead of using a hard auachme ntarou nd th e panel edges. engineersattached Vclcro-type Dual Lock stripsto allow fast attach men t and removalof panels and eliminate trimming .

Cos t of making the changes wasj us t over $400,000 , but the cos tavoidance with the new coc kpit ceil­ing is an estim ated $ 1,750.000 in the120-aircraft program . Moreover, theAir Force will requ ire less mai nte ­nan ce tim e over the next 20 yearswith the redesign. Othe r resu lts wereth at part cou nt d ro pp ed fro m 68 7pieces to 75 and that the fas te ne rcount is now about 400 ins tea d of2450. The redesign saved 25 lb (1 1kg), an d insta llation time fell from230 hr to less than 75 hr .

92 JULY 1 99G·MANU FACTURING ENGINEERING

More than 27.000 workers nationwide are involved in the building of 1:-17s.

on the bouorn of the aircraft to makeone lOX I T (3 X 5-m) panel. The newm el hod also included more chemicalmilli nv of the skin to produce thickerskin around I he maint enance hat ch

Quality Report Card™

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The Quality Report CardTN:(QRCTM) was developed basedon the six-sigma philosophyand records the inherentdefect rate designed into the

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'lrid" product. An itemized list ofall parts in the assembly

from Lean Design™ is used in conjunction withknown or pre-programmed PPM and warrantydata to capture defects, which will affectproduct Quality. The QRCTM highlights poor

quality drivers and ~;::=- :;-Pred ic t s first time ;;:~'::,',:,:,- ~.....' ~

capability on the factoryfloor or in the designstage. The QRCTM willquantify the cost of thehidden factory and willprioritize where the most savings can be found.

94Circle 1Ul JULY 1 996-MANUFACTURING ENGINEERING

Lean Design ™

94% Part Reduction$45,000,000 Saved

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Landing Gear Pod

C-17 Lean Deslgn" Successes

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Since 1988, M unr'o & Associates has been achange agent leading the industry to helpmanufactu..-e..-s ..-each thei..- p..-ofit potentials byimp..-oving thei..- enginee..-ing methods.C hanging the product design will ..-ipple downto all a..-eas of manufactu..-ing, thus imp..-ovingquality and p..-ofit d..-amatically.

Lean DesignTM is a

quantitative analyticalmethod used to map every

part, tool and ope..-at0..­-'-101'"--.' movement while challenging

each step to find the valuedand non-valued (g o o d vs. bad)parts and p..-ocesses. Althoughsoftwa..-e is used as a scoringaid, the "mi..-acle" is in theI'M!: r~igncnolOOd pL..~ ic Lean lJeBignml" p..-ocess and

methodology. New technologyis int..-oduced and the finalp..-oduct will CAlM +inurlf(C(l & w.ih

evolve tohave a ..-evolutionary newlook, less ope..-ations, simplerto build, imp..-oved quality andhave a d..-amatically lowe..- cost. The exampleshown in these few graphics migrates frOIDover 250 steps and 30 tools to 6 steps and 2tools using the Lean Design™ process and ourTechnology Transfer.

M A NUFACTURIN G ENGINEERING-J ULY 1 9 9 6

ADFMDoubleheaderSometimes, en gin eers performed

two re des ign p ro j ects in con cert .One example involved modi fying thewi ng-bo x asse m bly fixt ure an d thewing pylon stub suba ssembly, wh erevariables in the front wingspar affect­ed installation of the pylon stub .

Workers asse mble each wing ha lfwhile it is in a vertical posi tion andth en in s tall th e pylon st ub on thefront spa r. The problem with the ini­tial wing bo x tooling W,lS that it sup­ported the 9') · (29-rn)-long fron t spa rat on ly four po ints , which meant thespar could sag u p to 0.3" (8 mrn)during assembly . It also mean t tha tthe wing skin p anel requ ired trim­ming in the fixtu re to ensure a goodfit. Because of th e va riab il itv in th efront spar location, it was difficu lt toinstall the pylon stub without a lot ofrework. Op erators also ha d to assem­ble the pylon stub, with its mo re than100 detail pa rts, on the wing to elimi­nate the problems cause d by variabi l­ity. They also ha d to remove suppo rtsto install the upper sk in panel s , andthen reassem ble them.

The tool modificat ion re p lace dthe four su p ports with a large trussarrangement tha t suppo rted the frontspar at 17 point s , which red uced sagto le ss than 0.010' (0.3 m rn) . Inaddit ion , worke rs now hav e access toa dedicated in tern al crane sys tem toload upp er skins into the tuol withoutremoving the su pport . Th e truss alsop rev e n ts workc rs from u s ing th efront spar as a con venient wo rk plat­form,

Red ucing variation mack it easierto asse mble the pylon s tu b o ll' t hcwing with sepa rate toolin ,!!, and theninstall it as on e p iece. ;\ su bco ru rac­[O r aided the cos t red uct ion cllon bymach inin g th e cou nte rsin ks lur fas­ten ers in the titan iu m up per dou blerusi ng a five-a xis mach ine 100 1, wh ichel iminated a ma nual o pe ration.

The two proje cts combined savedtime In later positions on the assern­bly Iinc, c u ll ing the need to shim Ihefixed lead ing edges that attach to thefront spar a nd facil itat ing a fill in gope rat ion around the py lo n st ubs .The p roj ec ts a lso c h anged ma nyworke rs ' a ltitudes : th ey no lo nge rfed as though they have to make d uewit h ina deq uate tools. •